Localized heat applied to a site in a patient's body has often been used to Cauterize a lesion in order to stop bleeding. Localized heat can also be used to alter, remove, or destroy tissue in a patient's body. One example of the medical use of localized heating is in the treatment of a bleeding ulcer. An endoscope is inserted through a patient's esophagus to view the bleeding site and to guide an electric powered heating element to contact the site and cauterize the bleeding. Another example is the use of localized heating to remove neoplastic pulmonary tissue. Still another example is the use of such heating to cauterize the endometrium.
Unfortunately, electric heating elements can be both difficult to manipulate and slow heating. The heating rate and maximum sustainable temperature are limited by the electric current available to the element. The available current in turn is limited by the size of the wires leading to the element. Wire size limits access to body sites for two reasons: larger wires cannot be inserted into small areas, and increased wire size typically causes a loss of flexibility.
The electric current passing through the wires also limits the regions in the body in which such a device can be used. The current presents a threat of an electric shock to the patient. The electric field generated by flowing current can also have undesirable effects. One region where such an electric field could possibly be life threatening is in the heart.
One electrically heated medical device in which the end of an endoscope is heated to avoid dew forming on a window is shown in U.S. Pat. No. 4,279,246 to Chikama. That device heats the window to about body temperature to prevent dew formation. However, due to the design of the device, the heat generated on the window is limited to about body temperature and therefore cannot be used to alter or destroy tissue.
Another electrically heated medical device that becomes sufficiently hot so as to cauterize tissue is shown in U.S. Pat. No. 4,449,528 to Auth et al. A miniaturized, endoscopically deliverable thermal cautery probe is used to cauterize internal vessels. The probe is applied to tissues cold, and a large number of electric heating pulses of equal energy are then applied to an internal heating element within the probe. The probe's internal heating element is in direct thermal contact With an active heat-transfer portion that has a low heat capacity. The low heat capacity of the heat-transfer portion insures quick heating and subsequent cooling, thereby adequately coagulating tissue while minimizing heat penetration and resulting tissue damage.
Because of the difficulties with electrical heating, medical devices, systems and methods have been developed for applying localized heat that is generated otherwise than by routing an electric current to a site in a patient's body. The localized heat so generated can be used for several purposes. For example, it may be used to cauterize a lesion to stop bleeding, to remove a clot, or to remove an arteriosclerotic deposit from a blood vessel. The localized heat can also be used to create an open channel in a previously occluded blood vessel.
One medical device not employing electrical current for heating is described in U.S. Pat. No. 4,207,874 to Choy which discloses a laser tunneling device used to locate, analyze, illuminate and destroy obstructions in a lumen such as a blood vessel. The device includes a fiberoptics bundle in a flexible conduit that is insertable into the blood vessel. The conduit includes a connection to a suction source at one of its ends, a valved means of controlling the application of suction which also functions to control the injection of locating material, and a connection to the fiberoptics bundle. The fiberoptics bundle is divided into an illuminating source bundle portion, a viewing bundle portion and a laser bundle portion. The device functions to remove obstructions in tube structures of both biological and non-biological types by insertion of the conduit sheathed device into the tube structure in a position distal to the obstruction.
Still a further prior medical device contemplates use of a single fiberoptic light transmission path within a medical catheter device to be either a viewing system, a laser light transmitting system, or a combination of both. In U.S. Pat. No. 4,445,892 to Hussein et al., a dual balloon catheter device is shown to have two spaced and expandable balloons for occluding a segment of a blood vessel. An optic system is used in the segment for viewing or for delivering laser light. Both the viewing and the laser light delivery are through a circumferential window within the tubular structure of the catheter.
U.S. Pat. No. 4,646,737 to Hussein et al., describes a device that includes a heat-generating element mounted on the distal end of an elongated electromagnetic energy transmitting conduit or member. A preferred conduit is a single flexible quartz optical fiber. Electromagnetic energy in the form of visible light from an intense light source, such as a laser, is transmitted through the conduit and is emitted onto a light-receiving surface of the heat-generating element. The light is converted by the element to heat. The heated element is then placed in contact with material in a patient's body such as a clot, deposit or tissue. The heated elements alter the material by melting, removing or destroying it. The heat-generating element preferably has a rounded exterior surface end. It is typically retained on the conduit by a locking means, such as by a ridge on the element that is received in a complementary groove on the conduit.
Still other prior medical devices tunnel and cut bodily tissue and other material within the body by direct application high intensity, typically laser, light that is typically conducted through fiberoptics. Laser devices--the acronym "laser" indicating light amplification by the stimulated emission of radiation--are well known. Briefly, a laser device operates by using an intense source to cause ions to become inverted with respect to their normal energy distribution. The tendency of such ions is to relax to a so-called "ground state" (a normal distribution), and in so doing to stimulate inversion of other ions within the same wavelength. A synchronized output is promptly achieved wherein the ion's relaxations from an inverted energy state transpire in unison. A massive output of energy is thereby obtained. The output wavelength is determined by the difference between the energy level from which the ions relax and the ground state energy level which the relaxed ions assume.
The medical device shown in U.S. Pat. No. 3,315,680 to Silbertrust et al., describes a cauterizer using fiberoptic techniques to conduct ordinary and laser light in a medical application. U.S. Pat. No. 3,821,510 to Muncheryan shows the use of a laser system which accommodates fluid flow to control the temperature of the work area.
German Patent No. 2,826,383 to Eichler et al., shows a tubular probe for laser surgery that is placed against or inserted in tissue. In one embodiment, an end piece having an absorbent surface is heated by the beam while it is in contact with the tissue, thereby heating the tissue. Alternatively, in another embodiment, the end is transparent and permits the laser beam to pass through the end in order to radiatively heat the tissue.
These various types of prior medical devices do not permit that tissue destruction using the lateral direction of high intensity radiated light and using radiated and/or conducted heat should be performed closely proximately, or simultaneously, in time. This can be very useful when it is desired to destroy large surface areas of tissue to a substantial depth.
For example, a surgical procedure referred to as "endometrial ablation" has been recently developed as an alternative to hysterectomy for treatment of excessive uterine bleeding. In this procedure, an Nd:YAG laser is used to destroy the entire endometrium lining the uterus. An optical fiber is inserted in the uterus by means of a hysteroscope to conduct the laser energy to the endometrium. With the aid of a parallel optical viewing fiber of the hysteroscope, the end of the laser-transmitting fiber is slowly moved across the surface of the endometrium so that the laser energy penetrates and destroys the endometrium which is on the order of three millimeters thick. Typical prior art procedures have utilized a bare optical fiber for transmitting the laser energy. Two techniques have been developed. By one technique, the end of the bare optic fiber is actually touched to the endometrium. By a second technique, generally referred to as "blanching", the bare tip of the optic fiber is held several millimeters away from the endometrium. These techniques are generally described in Daniell et al., "Photodynamic Ablation of the Endometrium With the Nd:YAG Laser Hysteroscopically as a Treatment of Menorrhagia", Colposcopy & Gynecologic Laser Surgery, Vol. 2, No. 1, 1986; Mackety, "Alternative to Hysterectomy: Endometrial Albation by Laser Photovaporization", Today's OR Nurse, Vol. 8, No. 4; and Goldrath et al., "Laser photovaporization of endometrium for the treatment of menorrhagia", Am. J. Obstet. Gynecol., Vol. 140, No. 1, page 14, May 1, 1981.
Some surgeons prefer the "blanching" technique because it is believed to create fewer complications. There is less danger of mechanical perforation of the uterus. There is less actual vaporization and cutting of the endometrial tissue and accordingly less fluid absorption thereby.
It is difficult, however, to treat the side walls of the uterus by "blanching" due to lack of room to maneuver the optic fiber so as to direct it toward the side walls. Thus a touching or dragging technique has necessarily been utilized during those portions of the procedure. In addition to being unable to direct the laser energy directly at the side wall of the endometrium, this touching of the fiber tip to the endometrium is, as mentioned, considered undesirable by some surgeons.
Furthermore, with the touching technique, and to a lesser extent with the blanching technique, there is always the problem of completely treating the entire endometrium without missing small areas here and there.
Accordingly, it would be desirable if a medical device were available which would permit more of the laser energy to be directed transversely from the optical fiber toward the side wall of the endometrium. It would further be desirable to maintain some suitable spacing between the tip of the optic fiber and the endometrium. Also, it is desirable that heat be conductively applied to the endometrium while simultaneously directing the laser energy to a more localized spot thus better insuring destruction of the entire surface of the endometrium.
It would additionally be useful if the operative excising and cauterizing head of the device were to somehow be directional, as well as necessarily controllable, in one or both of its light radiation and/or its-conductive heating effects. A preferred operational direction of the device, operative head for either the lateral transmission of light or the conductive heating of tissue would permit that one effect could be maximized over the other by action of the surgeon's positioning and orientation of the device's operative head within the body cavity. Furthermore, a device exhibiting a preferred directionality would presumably exhibit some safe orientation in which orientation the device's operative head would not be prone to destroy and/or burn the lining of the body cavity within which it was situated.